This invention relates to a man-machine interface and in particular to an interface that provides tactile sensation to a user.
Virtual reality (VR) is an immersive environment which is created by a computer and with which users have real-time, multisensorial interactions. Typically, these interactions involve some or all of the human senses through either visual feedback, sound, force and tactile feedback (i.e. reflection), smell and even taste. The key to immersive realism is the capacity of the user to use his/her hand to interactively manipulate virtual objects. Unfortunately, the majority of existing commercial virtual reality systems use hand-sensing devices that provide no haptic feedback. Nevertheless, some efforts have been made to provide means for presenting force and tactile information to the user""s hand. By force information, it is meant the application of a set force to a selected part of the hand, for example, a finger. By tactile information, it is meant the application of a stimuli, e.g., a vibration, to a selected part of the hand, e.g., a fingertip pad. This stimulus, could simulate surface texture or dynamic conditions at the contact, for example. A few examples of existing force reflecting devices are the EXOS SAFiRE(trademark), the Master II Hand Master device at Rutgers university, the PERCRO Force-Reflecting Hand Master and the Sarcos TOPS Force-Reflecting Hand Master. Some tactile feedback devices that have been developed include the PERCRO Position-Sensing and Tactile Feedback Hand Master and the EXOS TouchMaster(trademark).
Virtual reality is not the only field where it is desirable to feed back force and tactile information to a human user/operator. Another common area is telerobotics. Some of the devices mentioned above are also often used as telerobotics interfaces. Some examples in the literature of feedback devices designed more specifically for telerobotics include the tactile shape sensing and display system developed by Kontarinis et al., the voice-coil based tactile feedback device used by Patrick et al. and the pin-based tactile display array developed by Kaczmarek and Bach-y-rita. Other applications for a vibrotactile unit of the subject invention include, but are not limited to, gesture recognition, music generation, entertainment and medical applications.
In an ideal case, it would be desirable to provide full force and tactile feedback to a user to make the virtual reality or telerobotic experience as realistic as possible. Unfortunately, most force feedback devices are cumbersome, heavy, expensive and difficult to put on and remove. Many of the tactile feedback solutions are also cumbersome, complex and fragile. Additionally, some of the tactile feedback devices described in the literature, such as small voice coils mounted to directly contact the skin, tend to numb the skin after only a few seconds of operation and then become ineffective as feedback devices.
An object of the invention is a man-machine interface which may be employed in such areas as interactive computer applications, telerobotics, gesture recognition, music generation, entertainment, medical applications and the like. Another object of the invention is a mass which is moved by a xe2x80x9cmass-moving actuatorxe2x80x9d which generates a vibration that a user can feel. Yet another object of the invention is the generation of an activating signal to produce the vibrations either as a result of the user""s state or as a result of environmental conditions, whether virtual or physical. Still another object of the invention is vibrating the bone structure of a sensing body part, as well as skin mechanoreceptors, to provide feedback. Yet still another object of the invention is the complex actuation of vibratory devices.
The tactile sensation that a user feels is generated by a vibrotactile unit mounted on, or in functional relation to, a sensing body part of a user by a fastening means. In one embodiment, the vibrotactile device comprises a mass connected eccentrically to a mass-moving actuator shaft (i.e. the center of mass of the mass is offset from the axis of rotation). Energizing the mass-moving actuator causes the shaft to turn, which rotates the eccentric mass. This rotating mass causes a corresponding rotating force vector. A rapidly rotating force vector feels to the user as a vibration. A slowly rotating force vector feels like a series of individual impulses. For a small number of rapid rotations, the rotating force vector feels like a single impulse. We will use the term xe2x80x9cvibrationxe2x80x9d to denote a change in force vector (i.e., direction or magnitude). Examples of vibrations include, but are not limited to a single impulse, a sinusoidal force magnitude, and other functions of the force vector. We use the term xe2x80x9ctactile sensationxe2x80x9d to refer to the feeling perceived by a user when their sensing body part experiences vibrations induced by a vibrotactile unit.
A signal processor interprets a state signal and produces an activating signal to drive the mass-moving actuator. The variable components of the state signal may be physical (e.g., measured), or virtual (e.g. simulated, or internally generated); they may vary with time (e.g., the state variables may represent processes); and they may be integer-valued (e.g., binary or discrete) or real-valued (e.g., continuous). The signal processor may or may not comprise a computer which interprets and further processes the state signal. The signal processor comprises a signal driver which produces an activating signal supplying power to, or controlling the power drawn by, the vibrotactile unit. The power may be, but is not restricted to, electric, pneumatic, hydraulic, and combustive types. The driver may be, but is not restricted to, an electric motor controller comprising a current amp and sensor for closed loop control, a flow valve controlling the amount of a pressurized fluid or gas, a flow valve controlling the amount of fuel to a combustion engine and the like. The details of such a signal processor and mass-moving actuator are common knowledge to someone skilled in the art.
The state signal may be generated in response to a variety of conditions. In one embodiment, one or more sensors measuring physical conditions of the user and/or the user""s environment may generate one or more components of a physical state signal. In another embodiment, a computer simulation may determine the one or more components of a virtual state signal from a simulated (e.g., virtual) state or condition. The virtual state may optionally be influenced by a physical state. The virtual state includes anything that a computer or timing system can generate including, but not restricted to, a fixed time from a previous event; the position, velocity, acceleration (or other dynamic quantity) of one or more virtual objects in a simulation; the collision of two virtual objects in a simulation; the start or finishing of a computer job or process; the setting of a flag by another process or simulation; combinations of situations; and the like. The virtual state signal is a machine-readable measurement of the virtual state variables.
The physical state signal is measured from physical state variables. These variables have relevance to the physical state of a body part of the user or the user""s physical environment. The physical state variables includes any measurable parameter in the environment or any measurable parameter relating to a body part of the user. Some examples of measurable physical parameters in an environment include but are not restricted to, the state of a body part, the position of objects in the environment, the amount of energy imparted to an object in the environment, the existence of an object or objects in the environment, the chemical state of an object, the temperature in the environment, and the like. The state of a body part may include the physical position, velocity, or acceleration of the body part relative to another body part or relative to a point in the environment. The state of a body part may also include any bodily function, where the measured state signal may include the output from an electroencephalograph (EEG), electrocardiograph (ECG), electromyograph (EMG), electrooptigraph (EOG) or eye-gaze sensor, and sensors which measure joint angle, heart rate, dermal or subdermal temperature, blood pressure, blood oxygen content (or any measurable blood chemical), digestive action, stress level, voice activation or voice recognition, and the like. The user""s voice may constitute a measured physical state variable, where his spoken words are sensed and/or recognized to generate a corresponding activating signal. The physical state signal is a machine-readable measurement of the physical state variables.
The state signal is presented to the signal processor which interprets the state, and then determines how and when to activate the vibrotactile units accordingly. The signal processor produces an activating signal which may be in response to an event it interprets from the state signal. Examples of events include contact, gestures, spoken words, onset of panic or unconsciousness, and the like. The interpretation of the state signal may or may not be a binary event, i.e. the simple changing of state between two values. An example of a binary event is contact vs. non-contact between two virtual or real objects. The process of interpreting may include any general function of state variable components. The interpretation function may produce an output control value which is integer or real-valued. A non-binary-valued interpretation output typically relates to the signal processor producing a non-binary activation signal.
By varying the functional form of the activation signal, the type of feedback that the vibrotactile device generates may also be varied. The device may generate a complex tactile sensation, which is defined to be a non-binary signal from a single or multiple vibrotactile units. Examples of complex tactile sensations include (1) varying the amplitude of vibration with a profile which is non-uniform over time; (2) varying the frequency of vibration; (3) varying the duration of impulses; (4) varying the combination of amplitude and frequency; (5) vibrating two or more vibrotactile units with a uniform or non-uniform amplitude profile; (6) sequencing multiple vibrotactile units with different amplitude or frequency profiles; and the like.
The frequency and amplitude of the vibration or impulse may be changed by modifying the activating signal to the mass-moving actuator. The frequency and amplitude may also be controlled by increasing the mass or by changing the radius of gyration (e.g. changing its eccentricity). For example, the mass may be changed by pumping fluid into an eccentrically rotating container. The sense of frequency that the user perceives may be changed independently of the amplitude by modulating the power to the vibrotactile unit at a variable frequency. This technique is called amplitude modulation, which is common knowledge to those skilled in the art. This change in frequency and amplitude may be used to convey complex, compound or other forms of information to the user.
Sensors may be mounted on the vibrotactile unit or the sensing body part to determine the frequency and amplitude of vibration sensed by the user. A feedback control loop may be added which uses this information to more tightly control the frequency and amplitude, or to reach peak efficiency at the resonant frequency of the collective vibrating device-body system.
Examples of a sensing body part on which the vibrotactile unit may be mounted, or in functional relation to the vibrotactile unit, include, but are not limited to: the distal part of a digit, the dorsal (back) side of a phalanx or metacarpus, palm, forearm, humerus, underarm, shoulder, back, chest, nipples, abdomen, head, nose, chin, groin, genitals, thigh, calf, shin, foot, toes, and the like. A plurality of vibrotactile units may be disposed on or near different sensing body parts, and may be activated in unison or independently.
Each vibrotactile unit may be affixed to the body by a fastening means. The fastening means is defined to be the means of attaching the vibrotactile unit to a sensing body part, transmitting (and possibly modifying) the vibrations created by the vibrotactile unit. This means may be one that is flexible such as a strap made of cloth or soft polymer, or rigid, such as metal or hard polymer which grabs or pinches the flesh, skin or hair. The fastening means may also include gluing or taping to the skin or hair, or tying with a string or rope around a limb, or attaching to clothes with VelcroTM or similarly functional means. A vibrotactile unit may also be attached to another structure which is then attached to the body part with the same means just mentioned. The vibrations generated by the actuator may be transmitted to the sensing body part by the structure (rigid or non-rigid), or through a linkage transmission or a fluid transmission.
The eccentric mass need not be mounted directly onto a motor shaft. A mechanical transmission may rotate the mass on a different shaft than the motor shaft. The mass-moving actuator rotates this shaft. Fluids such as air and liquids may also transmit the motion from a power source to the rotating eccentric mass. Changing magnetic fields may also be employed to induce vibration of a ferrous mass.
As previously mentioned, state signals may relate to a physical or virtual state. When the state represents a physical condition, the subject invention includes a state measurement sensor which produces a state signal. This state measurement sensor may measure some property of the sensing body part. Recall that the body part associated with receiving the vibrotactile stimulation is called the sensing body part, the body part associated with producing the activating signal is called the measured body part. The signal processor may receive signals from this sensor such as a tactile, position, bend, velocity, acceleration or temperature sensor and generate an activating signal. In this way, the user may receive feedback based on his actions or physical state. For example, the vibrotactile device may be used to train the user to do some physical motion task. In this case, the position or motion of the body part which is to do the motion task is measured by the state measurement sensor and is also the sensing body part. Direct stimulation to the body part being trained enhances the training of the task. Complex actuation in the form of a function of different levels of frequency or amplitude may inform the user whether his actions are correct or incorrect; the level of correctness may correspond to the level of frequency or amplitude.
In addition, the sensing body part (which is also the measured body part) may have a graphical representation shown to the user. The user may also be presented with visual, auditory, taste, smell, force and/or temperature cues to his actions in combination with the vibrotactile cues provided by the subject invention. The user may be immersed in a virtual environment. The user may see a graphical representation of his/her body part interact with virtual objects and simultaneously feel a corresponding tactile sensation simulating the interaction. For example a user may have his/her fingers be the sensing and measured body parts. The user may then see his/her virtual hand in the virtual environment contact a virtual object. The user would then feel an increasing vibratory stimulation on his/her physical fingertip as he increased the virtual pressure on the virtual object using the virtual fingertip.
As previously discussed, using the vibrotactile device of the subject invention, a user may receive tactile sensations based on the state of his body parts. In the previous case the state included the position, and other dynamic quantities, of the body parts. In certain applications, the measured body part is the same as the sensing body part (the list of possible sensing body parts mentioned earlier also applies to measured body parts); in other applications they are different body parts. When the measured body part is different than the sensing body part, the subject invention acts as a coupling device which relates the sensing body part and the measured body part.
In another application, the user may receive tactile feedback as a result of the conditions of a computer simulated environment, not necessarily related to the user""s actions or state. The vibrotactile units with varying actuation levels may be used to simulate a variety of contact situations, e.g., contact with fluids and solids, and contacts which are momentary or continuous. For example, a user immersed in a computer simulated virtual environment may feel simulated fluid (like air or water) across his body. In such a simulation, an array of vibrotactile units may vibrate in sequence to correspond to a pressure wave hitting the corresponding parts of the body; the amplitude of the vibration may vary to correspond to different levels of pressure being simulated. A user may also feel a virtual object that comes into contact with a portion of his virtual body. The user may feel a virtual bug crawl up his virtual arm by sequencing an array of vibrotactile units. To accompany the tactile sensations received by the user which are uncorrelated with his actions, the user may be presented with visual, auditory, taste, smell, force, temperature and other forms of feedback in order to enhance the realism of the simulated environment.
In yet another application of the vibrotactile device, a group of users may receive tactile sensations. In one example, users may wear individual vibrotactile units, or they may also share vibrotactile units as follows. A tactile sensation may be shared by one or more users making physical contact with the sensing body part of another user. For example, one user may wear vibrotactile units on the backs of his fingers. A second user, not wearing any vibrotactile units, may obtain vibrotactile feedback transmitted via the first user when the first user places the palmar side of his fingers on a sensing body part of the second user. The activating signal for each vibrotactile unit may be computer controlled via either user""s actions or through a computer simulated event. In a second example, a group of users may each receive identical tactile feedback through individually mounted vibrotactile units. The common activating signal may correspond to measured body parts from a single, optionally separate, user. Different users may also be responsible for producing the common activating signal for one or more vibrotactile units. For instance, the movement of one user""s arm may control the vibrotactile unit on each user""s arm; and the voice of a second user may control the vibrotactile unit on each user""s back; the eye-gaze of three other users may control the vibrotactile unit upon which they stare in unison. An example application of a single user controlling many user""s vibrotactile sensations is a new form of entertainment where a performer creates vibrotactile sensations for an audience.
In a preferred embodiment, the vibrotactile units are affixed to an instrumented glove, such as the CyberGloveTm manufactured by Virtual Technologies of Palo Alto, Calif., USA. The CyberGlove has sensors in it which measure the angles of the joints of the hand. The fingertips of the CyberGlove are open so that the user may reliably handle physical objects while wearing the glove. The open fingertips allow the user to feel the sensations of real objects in conjunction with the generated vibrotactile sensations. The fingertips need not be open, they may be fully enclosed as in the 22-sensor model of the CyberGlove. The mass-moving actuator of each vibrotactile unit is encased in a cylindrical housing and mounted onto the glove on each of the fingers and thumb, and on the palmar side of the hand. Each mass-moving actuator is composed of a small DC motor with an eccentric mass mounted rigidly onto the shaft of the motor. The casing is made of tubular plastic and serves to protect the motion of the mass from the user and protect the user from the rotating mass. The casing may be made of any rigid or semi-rigid material including but not limited to steel, aluminum, brass, copper, plastic, rubber, wood, composite, fiberglass, glass, cardboard, and the like. The casing may form a solid barrier, a wire-mesh, grid or column-like support capable of transmitting vibrations from the mass-moving actuator to the fastening means. The instrumented glove informs a computer of the position of the user""s hand and fingers. The computer, which is part of the signal processor, then interprets this hand state signal (and any virtual state signal if the application calls for it). The computer then generates a control signal, which when processed by the driver, activates the actuators to create tactile sensations.
One feature of the embodiment of the subject invention just described, which employs an eccentric mass, is that the energy imparted into the system can be less than the energy required when using electromagnetic coils (such as the speaker voice coils used by Patrick et al. and the EXOS TouchMaster). Energy is stored as rotational inertia in the eccentric mass, whereas the voice-coil-based systems lose all inertial energy each time the coil change directions.
Another feature of the subject invention is that vibrating the bone structure of a body part, as well as skin mechanoreceptors, has an advantage over stimulating just the skin mechanoreceptors (such as Meissner, Merkel, Ruffini and Pacinian corpuscles) in that the nerves do not get easily overstimulated and do not become numb. In addition, the form of information to the user is closer to a physical contact sensation where the muscles and joints are stimulated, as is done by full force feedback systems. As a result, the vibrotactile units need not be attached to a body part which has sensitive skin mechanoreceptors. For example, a vibrotactile unit may be attached to a fingernail or an elbow.
In an embodiment in which a user is immersed in a computer simulated environment, actuation of vibrotactile units can approximate the sensation of touching physical objects as full force feedback devices do. The deep impulsive sensation in the muscles and joints generated by the vibrotactile units simulates the change in proprioceptive state as the user touches a virtual object. The subject invention provides numerous advantages over a sustained force feedback device. For example, because of its simplicity, the vibrotactile device of the subject invention can be made smaller, lighter, less encumbering, more robustly and cheaper.
The subject invention may be used in combination with a sustained force feedback device as provided by Kramer in U.S. Pat. No. 5,184,319, Kramer in U.S. patent application Ser. No. 08/373,531 (allowed), Zarudiansky in U.S. Pat. No. 4,302,138, Burdea in U.S. Pat. No. 5,354,162, and Jacobus in U.S. Pat. No. 5,389,865. These patents and patent applications are incorporated herein by reference. Such a combination can give a higher frequency response than that capable of being generated by the sustained force feedback device and/or to reduce the cost and/or size of the full system. The subject invention may also be used in combination with other tactile feedback devices such as heating or cooling devices, bladder devices or voice coils.